In the above prior application, a tank liquid level measuring system is disclosed in which atmospheric air is simultaneously pumped through a submerged purging tube extending to a point near the bottom of a liquid storage tank and into the bellows compression chamber of a gage which is calibrated to indicate the depth of liquid in the tank in inches or other units. The pumping of atmospheric air is continued until the gage needle falters, indicating that the tube within the tank has been purged or evacuated of liquid, and a balanced pressure condition has been established between the head of liquid in the tank and the instrument compression chamber.
The above system, while capable of many uses, is particularly adaptable to monitoring the levels of gasoline in underground storage tanks in filling stations.
One important problem which the system in the prior application cannot deal with is the problem caused by the accumulation of water near the bottom of the tank beneath the lighter gasoline. Water contamination of gasoline in storage tanks is presently costing the oil companies large sums of money each year in consumer lawsuits and automobile repairs.
With this problem in mind, the objective of the present invention is to provide a simplified and reliable means in the nature of an attachment to the above-referenced system to detect the presence of water in gasoline storage tanks and to indicate directly to the filling station operator at an instrument in his office that the fuel contamining water is present in the bottom of the tank.
While this is the principal intended use of the invention, it is equally applicable to many other situations where liquids of different specific gravities are present in the storage vessel and it is desired to detect and indicate the presence of the heavier liquid in the bottom of the tank below the lighter liquid.